1. Field of the Invention
The present invention generally relates to a device and method that control the engagement speed of a clutch. More particularly, the present invention relates to such a device and method as they are employed on a straddle-type vehicle.
2. Description of the Related Art
Vehicles can have any of a number of different transmission types. Three types of shiftable transmissions are a manual transmission, a semi-automatic transmission in which clutch manipulation by a rider is not required for shifting and an automatic transmission. These types of transmissions generally comprise a clutch.
As is known, a clutch generally is used to interrupt the flow of power from an engine output to a transmission input. As such, the clutch typically comprises a drive member on the engine side and a driven member on the output side. When the driven member and the drive member are brought together, the clutch is considered engaged. When the driven member and the drive member are separated, the clutch is considered disengaged. The clutch typically is engaged and disengaged with an engagement device that uses a clutch actuator to bring the drive member and the driven member into engagement.
Some clutch engagement devices feature two or three different speeds at which the clutch is engaged in order to improve the feel of the engagement action while shortening the time for engagement to occur. For example, if the clutch is moving from a disengaged state to a semi-engaged state, engagement may occur rapidly by forcing the drive side and the driven side of the clutch together at a high speed. Once the clutch has become semi-engaged, the clutch engagement proceeds at a low speed from semi-engagement to engagement until a clutch rotating speed difference becomes less than or equal to a predetermined value. The low speed movement from the semi-engaged state to the engaged state reduces an impact between the drive side and the driven side, which reduction results in a more comfortable operation for the rider.
To shorten the time required to achieve engagement, some clutches, once semi-engaged, continue to bring the drive-side and the driven-side together at a high speed once a clutch rotating speed difference becomes less than or equal to the predetermined value. Such configurations can be found, for instance, in JP-A-2001-146930 and JP-A-2001-173685.
While such constructions bring the drive member and the driven member together at different speeds during the range of movement, these speeds do not vary based upon the difference in rotational speeds of the drive member and the driven member (i.e., a clutch rotating speed difference). For instance, while the clutch rotating speed difference gradually varies over time during engagement of the clutch, two or three preset clutch engagement speeds are maintained until a clutch rotating speed difference becomes less than or equal to a predetermined value without adjusting the clutch engagement speed according to the difference in the rotational speeds of the two members.
Therefore, conventional clutch connection devices do not respond in different ways to different operational demands. The drive member and the driven member are brought together at the same two or three speeds regardless of the operating conditions. For example, quick braking and/or quick throttle operation of a vehicle by a rider while engaging the clutch is treated the same as an ordinary clutch engagement.